In 1900, El Paso became the scene of intense recruitment efforts of Mexican workers as American railway companies struggled to fill their labor needs. Asian immigrants had provided much of the building labor on the first transcontinental railroad, but the Chinese Exclusion Act of 1882 restricted immigration from China. US railroad companies, which had done extensive work in Mexico, encouraged the immigration. Southern Pacific and the Atchison, Topeka and Santa Fe Railroads hired the most Mexicans, giving them six-month contracts to lay track in California. By one estimate, 16,000 Mexicans were working on the railroad in the Southwest and West by 1908; the number of Mexicans hired for rail work peaked between 1910 and 1912.